Method and system for operating a near-to-eye display

ABSTRACT

Methods and systems for operating a vehicular near-to-eye (NTE) display screen operable within an operational range limit are provided. An image is rendering on the NTE display screen within a predefined visibility range. The predefined visibility range is within the operational range limit. A luminance of at least a portion of the image is reduced in response to the NTE display screen being moved outside of the predefined visibility range and within the operational range limit.

RELATED APPLICATIONS

This application claims the benefit of U.S. application Ser. No.12/137,271 (U.S. Pat. No. 8,416,152) filed Jun. 11, 2008, which ishereby incorporated by reference.

TECHNICAL FIELD

The present invention generally relates to head-up displays (HUDs), andmore particularly relates to methods and systems for operatingnear-to-eye (NTE) displays.

BACKGROUND

Modern vehicles, such as aircraft, often include head-up displays (HUDs)that project various symbols and information onto a transparent display,or image combiner, through which a user (e.g., the pilot) maysimultaneously view the exterior. Traditional HUDs incorporate fixedimage combiners located above the instrument panel on the windshield ofthe aircraft, or directly between the windshield and the pilot's head.

“Head-mounted” HUDs have been developed that utilize image combiners,such as near-to-eye (NTE) displays, coupled to the helmet or headset ofthe pilot that move with the changing position and angular orientationof the pilot's head. Although an advantage of head-mounted HUDs is thatthe information displayed may be visible to the pilot regardless of theposition or orientation of his or her head, there may circumstances inwhich the pilot would prefer that the information on the NTE display notbe visible, such as when the pilot is attempting to view the terrainwith as little visible obstruction as possible, or when the pilot isviewing a display on the instrument panel (i.e., a “head-down” display).

In this sense, traditional HUDS utilizing fixed image combiners offerthe advantage that the information displayed is typically only visiblewhen the pilot's head is directly in front of the image combiner. Thatis, if the pilot leans to the side to look around the image combiner, orlooks down at the instrument panel, the information on the HUD is nolonger visible.

Accordingly, it is desirable to provide a method and system foroperating a NTE display in such a way to improve the user's control overwhen the information is displayed. Furthermore, other desirable featuresand characteristics of the present invention will become apparent fromthe subsequent detailed description of the invention and the appendedclaims, taken in conjunction with the accompanying drawings and thisbackground of the invention.

BRIEF SUMMARY

A method for operating a vehicular near-to-eye (NTE) display screenoperable within an operational range limit is provided. An image isrendering on the NTE display screen within a predefined visibilityrange. The predefined visibility range is within the operational rangelimit. A luminance of at least a portion of the image is reduced inresponse to the NTE display screen being moved outside of the predefinedvisibility range and within the operational range limit.

A method for operating a near-to-eye (NTE) display screen operablewithin an operational range limit on-board an aircraft is provided. Afirst image is caused to be rendered on the NTE display screen within apredefined visibility range. The first image is at least representativeof a field of view of a user on-board the aircraft, and the predefinedvisibility range is within the operational range limit and a function ofat least three degrees of freedom. A second image is rendered over thefirst image on the NTE display screen. A luminance of at least a portionof the second image is reduced in response to the NTE display screenbeing moved outside of the predefined visibility range and within theoperational range limit.

An avionics system is provided. The avionics system includes a headset,a tracking system, and a processor. The headset is configured to be wornon a head of a user and includes a frame and a near-to-eye (NTE) displayadjustably coupled to the frame to be positioned proximate to an eye ofthe user. The NTE display is operable within an operational range limiton-board an aircraft. The tracking system is configured to detect atleast one of a position and an angular orientation of the NTE display.The processor is in operable communication with the NTE display and thetracking system. The processor is configured to render an image on theNTE display screen within the predefined visibility range, thepredefined visibility range being within the operational range limit,and reduce a luminance of at least a portion of the image in response tothe NTE display screen being moved outside of the predefined visibilityrange and within the operational range limit.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and

FIG. 1 is a schematic block diagram of an aircraft, according to oneembodiment of the present invention;

FIG. 2 is an isometric view of a headset on-board the aircraft of FIG.1, including a near-to-eye (NTE) display, centered within apredetermined visibility range;

FIG. 3 is a plan view of the NTE display with a symbology image renderedthereon;

FIG. 4 is an isometric view of the headset moved towards a side of thevisibility range;

FIG. 5 is a plan view of the NTE display with a portion of the symbologyimage dimmed;

FIG. 6 is an isometric view of the headset moved farther towards theside of the visibility range;

FIG. 7 is a plan view of the NTE display with an increased portion ofthe symbology image dimmed;

FIG. 8 is a plan view of the NTE display with the entire symbology imagedimmed;

FIG. 9 is an isometric view of the headset moved towards an opposingside of the visibility range;

FIG. 10 is a plan view of the NTE display with a portion of thesymbology image dimmed; and

FIG. 11 is a plan view of the NTE display with the entire symbologyimage partially dimmed simultaneously

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, and brief summary or the following detailed description. Itshould also be noted that FIGS. 1-11 are merely illustrative and may notbe drawn to scale. Additionally, in several of the drawings, a Cartesiancoordinate system, including x, y, and z axes and/or directions, isshown to clarify the relative position and/or orientation of thecomponents, according to the various embodiments. However, thiscoordinate system is only intended to assist in the explanation ofvarious aspects of the present invention, and should be not construed aslimiting.

FIG. 1 to FIG. 11 illustrate a method and system for operating avehicular near-to-eye (NTE) display screen. The NTE display is operablewithin an operational range limit, such as a flight deck on an aircraft.An image is rendered on the NTE display screen within a predefinedvisibility range which is defined by, for example, a range of positionsand/or angular orientations of the NTE display (or a headset to whichthe NTE display is coupled) within the operational range limit. Theimage is dimmed, or removed from the NTE display completely, in responseto the NTE display screen (and/or the headset) being moved outside ofthe predefined visibility range while still being within the operationalrange limit.

FIG. 1 schematically illustrates a vehicle 20, such as an aircraft,according to one embodiment of the present invention. The vehicle 20 maybe, in one embodiment, any one of a number of different types ofaircraft such as, for example, a private propeller or jet engine drivenairplane, a commercial jet liner, or a helicopter. In the depictedembodiment, the vehicle 20 includes a flight deck 22 (or cockpit) and anavionics/flight system 24. Although not specifically illustrated, itshould be understood that the vehicle 20 also includes a frame or bodyto which the flight deck 22 and the avionics/flight system 24 areconnected, as is commonly understood. It should also be noted thatvehicle 20 is merely exemplary and could be implemented without one ormore of the depicted components, systems, and data sources. It willadditionally be appreciated that the vehicle 20 could be implementedwith one or more additional components, systems, or data sources.

The flight deck 22 includes a user interface 26, display devices 28(e.g., a primary flight display (PFD)), a communications radio 30, anavigational radio 32, an audio device 34, a headset 36, and a head(and/or eye) motion tracker 38.

The user interface 26 is configured to receive input from a user 40(e.g., a pilot) and, in response to user input, supply command signalsto the avionics/flight system 24. The user interface 26 may includeflight controls (not shown) and any one of, or combination of, variousknown user interface devices including, but not limited to, a cursorcontrol device (CCD), such as a mouse, a trackball, or joystick, and/ora keyboard, one or more buttons, switches, or knobs. In the depictedembodiment, the user interface 26 includes a CCD 42 and a keyboard 44.The user 40 uses the CCD 42 to, for example, move a cursor symbol on thedisplay devices 28, and use the keyboard 44 to, for example, inputtextual data.

Still referring to FIG. 1, the display devices 28 are used to displayvarious images and data, in graphic, iconic, and/or textual formats, andto supply visual feedback to the user 40 in response to the user inputcommands supplied by the user 40 to the user interface 26. It will beappreciated that the display devices 28 may each be implemented usingany one of numerous known displays suitable for rendering image and/ortext data in a format viewable by the user 40, such as a cathode raytube (CRT) displays, a LCD (liquid crystal display), or a TFT (thin filmtransistor) displays. The display devices 28 may also be implemented onthe flight deck 22 as “head-down” displays or a head-up display (HUD)projection on a fixed image combiner.

The communication radio 30 is used, as is commonly understood, tocommunicate with entities outside the vehicle 20, such as air-trafficcontrollers and pilots of other aircraft. The navigational radio 32 isused to receive from outside sources and communicate to the user varioustypes of information regarding the location of the vehicle, such asGlobal Positioning Satellite (GPS) system and Automatic Direction Finder(ADF) (as described below). The audio device 34 is, in one embodiment,an audio speaker mounted within the flight deck 22.

The headset 36 includes an interconnected combination of earphones 46, amicrophone 48, and a near-to-eye (NTE) display (or display screen) 50.The earphones 46 may substantially form a frame for the headset 36 andbe configured to be removably worn by the pilot. The earphones 46 andthe microphone 48 may be in operable communication with thecommunications radio 30, and the NTE display may be in operablecommunication with the avionics system 24, as described below. The NTEdisplay 50 may be adjustably suspended from the earphones 46 such thatthe display 50 may positioned directly in front of an eye of the user 40while the headset 36 is worn, as is commonly understood. In oneembodiment, the NTE display 50 is an image combiner (i.e., asubstantially transparent plate), as is commonly understood. The NTEdisplay 50 may also be, for example, a flat panel display screen, suchas an LCD display screen. Although not shown, the headset 36 may alsoinclude an eye motion detector to detect movement of the eye of the userrelative to the user's head. Additionally, the headset 36 may includevarious hardware, such as inertial sensors, to detect movements of theuser's head. It should also be noted that the flight deck 22 may definean “operational range limit” of the headset 36, and in particular, ofthe NTE display 50. That is, the headset 36 and the NTE display 50 maynot be able to operate properly and/or communicate the other componentsof the aircraft 20 if removed from the operational range limit (e.g.,because the headset becomes “unplugged.”)

The motion tracker 38 is configured to detect (either solely or incombination with the hardware in the headset 36) movements (i.e.,position and angular orientation) of the pilot's head, the headset 36 asa whole, and/or the NTE display 50. Although not shown, the motiontracker 38 may utilize various methods to determine the movementsincluding optical and/or infrared components and inertial sensorslocated within the headset 36. Referring to FIGS. 1 and 2, the motiontracker 38 and/or the headset 36 (and/or the processor described below)define a “predetermined visibility range” (or eye-motion box) 52 locatedon the flight deck 22. Although shown as a cubic volume, the visibilityrange 52 corresponds to both a spatial and angular position of theheadset 36 and/or the NTE display 50 relative to the Cartesiancoordinate system shown. That is, the visibility range 52 defines arange of positions along the x, y, and z-axes shown and/or a range ofangular orientations about the x, y, and z-axes (i.e., six degrees offreedom) which is used to control the NTE display 50, as described ingreater detail below.

As shown in FIG. 1, the avionics/flight system 24 includes a runwayawareness and advisory system (RAAS) 54, an instrument landing system(ILS) 56, a flight director 58, a weather data source 60, a terrainavoidance warning system (TAWS) 62, a traffic and collision avoidancesystem (TCAS) 64, a plurality of sensors 66 (e.g., a barometric pressuresensor, a thermometer, and a wind speed sensor), one or more terraindatabases 68, one or more navigation databases 70, a navigation andcontrol system (or navigation computer) 72, and a processor 74. Thevarious components of the avionics/flight system 24 are in operablecommunication via a data bus 76 (or avionics bus). Although notillustrated, the navigation and control system 72 may include a flightmanagement system (FMS), a control display unit (CDU), an autopilot orautomated guidance system, multiple flight control surfaces (e.g.,ailerons, elevators, and a rudder), an Air Data Computer (ADC), analtimeter, an Air Data System (ADS), a Global Positioning Satellite(GPS) system, an automatic direction finder (ADF), a compass, at leastone engine, and gear (i.e., landing gear).

The processor 74 may be any one of numerous known general-purposecontroller or an application specific processor that operates inresponse to program instructions, such as field programmable gate arrays(FPGAs), application specific integrated circuits (ASICs), discretelogic, microprocessors, microcontrollers, and digital signal processors(DSPs), or combinations thereof In the depicted embodiment, theprocessor 74 includes on-board RAM (random access memory) 78 andon-board ROM (read only memory) 80. The program instructions thatcontrol the processor 74 may be stored in either or both the RAM 78 andthe ROM 80. For example, the operating system software may be stored inthe ROM 80, whereas various operating mode software routines and variousoperational parameters may be stored in the RAM 78. The RAM 78 and/orthe ROM 80 may include instructions stored thereon for carrying out themethods and processes described below. It will be appreciated that thisis merely exemplary of one scheme for storing operating system softwareand software routines, and that various other storage schemes may beimplemented. It will also be appreciated that the processor 74 may beimplemented using various other circuits, not just a programmableprocessor. For example, digital logic circuits and analog signalprocessing circuits could also be used.

During operation of the aircraft 20, the headset 36 is worn by the pilot40 (or other user), and the earphones 46 and the microphone 48 are usedto communicate with ground personnel, as well as other aircraft.Additionally, the NTE display 50 is adjusted such that it is positioneddirectly in front of one of the user's 40 eyes.

FIG. 3 illustrates the NTE display 50 during operation. On the NTEdisplay 50 are shown a terrain image 82 and a symbology image (or simply“symbology”) 84. The terrain image 82 is at least representative of thepilot's view from the flight deck 22. In the exemplary embodiment shownin FIG. 3, the terrain image 82 depicts a perspective view from theaircraft 20 of the terrain outside the aircraft 20 and coverssubstantially the entire display 50. The terrain image 82 includes aterrain portion 86 and a sky portion 88. As is commonly understood, inan embodiment in which the display 50 is an image combiner, the terrainimage 82 is simply the pilot's 40 view of the terrain (and/or theinterior of the flight deck 22) as seen through the NTE display 50.While, in an embodiment in which the NTE display 50 is, for example, anLCD display, the terrain image 82 is generated based on multiplereadings from various instruments onboard the aircraft 20 that provide acurrent position and/or orientation (e.g., heading) of the aircraft 20and changes as the position and/or orientation of the aircraft 20changes, as well as the terrain and navigational databases 68 and 70(FIG. 1). As indicated on FIG. 3, terrain features (e.g., hills,mountains, valleys, etc.) may be shown on the terrain image 82 to assistthe user 40 with the operation of the aircraft 20.

Still referring to FIG. 3, the symbology 84 is displayed over terrainimage 100. The symbology 84 includes multiple digital instruments, suchas an altitude indicator 90, an airspeed indicator 92, a headingindicator 94, a roll indicator 96, and a pitch indicator 98. In theembodiment illustrated, the altitude indicator 90 and the airspeedindicator 92 are displayed as an altitude “tape” and an airspeed tape,respectively, as is commonly understood. The heading indicator 94 isgraphically displayed as a compass at a lower center portion of thedisplay 50. The roll indicator 96 is displayed above the headingindicator 94 at an upper portion of the display 50, and the pitchindicator 98 is positioned between the heading indicator 94 and the rollindicator 96. The digital instruments 90-98 provide an indication of aposition and/or orientation (i.e., heading, pitch, roll, etc.) of theaircraft 20 to the user 40. As shown, the NTE display 50 also includes ahorizon bar 100, which may be considered to be part of either theterrain image 82 or the symbology image 84, or alternately part ofneither. The horizon bar 100 extends horizontally near the center of thescreen 50, through the pitch indicator 98.

In one embodiment, portions of the symbology image 84 are partially (orcompletely) dimmed based on the position and/or orientation of the NTEdisplay 50 (and/or the headset 36) relative to the predeterminedvisibility range 52. FIG. 2 illustrates the headset 36 (along with theNTE display 50) positioned, both spatially and angularly, approximatelyin the center of the visibility range 52 (e.g., with the pilot's headcentered above the pilot's seat and facing directly towards the front ofthe aircraft 20). As described briefly above, although the visibilityrange 52 is shown as a substantially cubic volume, it may represent botha spatial and/or an angular range for the operation of the NTE display50, according to one embodiment of the present invention. As such, thevisibility range 52 has first and second lateral limits 102 and 104 andfirst and second vertical limits 106 and 108, as well as a forward limit110 and a backward limit 112. Each pair of limits lies on opposing sides(or extrema) of the respective degree(s) of freedom. In an embodiment inwhich spatial limits are used, the visibility range 52 is a cubic spacehaving dimensions of, for example, 4×8×12 inches. In one embodiment,when the headset 36 is centered as shown in FIG. 2, the entire symbologyimage 84 is rendered on the NTE display 50 as shown in FIG. 3.

FIG. 4 illustrates the headset 36 moved along the x-axis towards thefirst lateral limit 102 of the visibility range 52, as well as rotatedabout the y-axis towards the first lateral limit 102. Referring to FIG.5, as the headset 36 approaches the first lateral limit 102, thesymbology image 84 is laterally divided into a first portion 114 and asecond portion 116 by, for illustrative purposes, dashed line 118. Thefirst portion 114 is adjacent to a first side 120 of the symbology image84, and the second portion 116 is adjacent to a second side 122 of thesymbology image 84. As shown, the first portion 114 of the symbologyimage 84 (excluding the horizon bar 100) is partially reduced inluminance (or removed completely), despite the fact that the NTE display50 is still within the operational range limit (i.e., the flight deck 22shown on FIG. 1).

FIG. 6 illustrates the headset 36 moved farther towards (and/or through)the first lateral limit 102 of the visibility range 52. Referring toFIG. 7, as the headset 36 is moved farther towards the first laterallimit 102 of the visibility range 52, the dashed line 118 traverses theNTE display 50 from the first side 120 of the symbology range 84 towardsto the second side 122 of the symbology image 84. As such, the firstportion 114 of the symbology image 84 has increased in size, while thesecond portion 116 has decreased in size. Thus, the portion of thesymbology image 84 that has been dimmed (or completely removed) hasincreased. FIG. 8 illustrates the NTE display 50 with the headset 36(amd/or the NTE display 50) moved completely through, or nearlycompletely through, the first lateral limit 102 of the visibility range52. As shown, the dashed line 118 has moved across the NTE display 50 tothe second side 122 of the symbology 84. As such, the second portion 116of the symbology image 84 has been completely removed, or nearlycompletely removed. In one embodiment, when the lateral limit 102 hasbeen exceeded, only the first portion 114 of the symbology image 84remains and occupies the NTE display 50. As a result, the entiresymbology image 84 has been dimmed (or removed) such that the pilot mayview the terrain image 82 and/or the interior of the flight deck 12 withno visible obstruction from the symbology image 84.

FIG. 9 illustrates the headset 36 moved along the x-axis towards thesecond lateral limit 104 of the visibility range 52, as well as rotatedabout the y-axis towards the second lateral limit 104. Referring to FIG.10, as the headset 36 approaches the second lateral limit 104, thesymbology image 84 is again laterally divided into the first portion 114and the second portion 116 by the dashed line 118. However, the firstportion 114 is now adjacent to the second side 122 of the symbologyimage 84, and the second portion 116 is adjacent to the first side 120of the symbology image 84. Again, the first portion 114 of the symbologyimage 84 is partially dimmed (or erased completely). As the headset 36is moved farther towards and/or through the second lateral limit 104,the dashed line 118 traverses across the NTE display 50 towards thefirst side 120 of the symbology image 84 in a manner similar to thatdescribed above.

Thus, the orientation of the dashed line 118 and the direction in whichthe dashed line 118 traverses the NTE display 50 is dependent upon thedirection in which the headset 36 and/or the NTE display 50 is movedwithin the visibility range 52. As another example, although notspecifically shown, the dashed line 118 may divide the symbology image84 in portions other than lateral portions. That is, if the headset 36is moved spatially and/or angularly downwards to (or through) the firstvertical limit 106 (FIG. 2), the dashed line 118 may extend horizontallyacross the NTE display 50 to divide the symbology image 84 into verticalportions such that the symbology image 84 is dimmed (or removed) from abottom side 124 of the symbology image 84 to a top side 126 of thesymbology image 84 (FIG. 5). Likewise, if the headset 36 is movedspatially and/or angularly upwards to (or through) the second verticallimit 108 (FIG. 2), the dashed line 118 may extend horizontally acrossthe NTE display 50 and the symbology image 84 may be dimmed (or removed)from the top side 126 to the bottom side 124 of the symbology image 84.

Again, it should also be understood, as described above, that thevisibility range 52 as defined by the motion tracker 38 and/or theheadset 36 may operate as both a function of the position of the headset36, as well as the angular orientation of the headset 36. As such, onlyangular movement of the headset 36 may be necessary to cause thesymbology image 84 to be dimmed or completely removed. For example, ifthe headset is rotated (e.g., 10-90 degrees) downwards about the x-axis,without changing spatial position within the visibility range 52, thesymbology image 84 may be completely removed as shown in FIG. 8.

In one embodiment, when the headset 36 is moved towards and/or throughthe forward limit 110 or the backward limit 112 (shown in FIG. 2) theentire symbology image 84 (or a portion thereof) is simultaneouslydimmed, as shown in FIG. 11. This dimming may occur gradually as theheadset 36 and/or the NTE display 50 is moved through the forward andbackward limits 110 and 112. For example, as the headset 36 passesthrough the forward limit 110, the entire symbology image 84 may bedimmed a first degree (e.g., from 100% luminance to 75% luminance). Asthe headset 36 continues to be moved out of the visibility range 52, theentire symbology image 84 may be dimmed a second degree (e.g., 75%luminance to 50% luminance), until the symbology image 84 has beencompletely removed as shown in FIG. 8. The symbology image 84 maysimilarly be dimmed as the headset 36 passes through the backward limit110 of the visibility range 52.

In another embodiment, as the headset 36 is moved towards and/or throughany of the limits 102, 104, 106, 108, 110, and 112 (FIG. 2), the entiresymbology image 84 is simultaneously dimmed as just described. Forexample, when the headset 36 is moved as shown in FIG. 4, the entiresymbology image 84 may be dimmed a first degree (e.g., from 100%luminance to 75% luminance). As the headset 36 continues to be moved outof the visibility range 52, such as shown in FIG. 6, the entiresymbology image 84 may be dimmed a second degree (e.g., 75% luminance to50% luminance), until the symbology image 84 has been completely removedas shown in FIG. 8.

One advantage of the method and system described above is that the pilotis, in effect, is able to “look around” the symbology displayed on theNTE display by moving his or her head. Thus, the pilot may view theexterior of the aircraft with a completely unobstructed view. Anotheradvantage is that the pilot is given the ability to disable thesymbology on the NTE display without manually actuating any user inputdevices on the flight deck (e.g., such as when the pilot wishes toquickly glance at one of the heads-down displays on the flight deck).

While the above embodiments have been described in the context ofrelatively straightforward defined visibility ranges, it should beunderstood that the general case of the present invention allows eachportion of the displayed image to be subject to its own definedvisibility range which is a generalized function of all applicabledegrees of freedom. Each defined visibility range may be made up ofmultiple constituent defined visibility ranges which may or may notintersect. As an exemplary embodiment, the defined visibility rangedepicted in FIG. 2 may have a central portion which is excluded, wherethe nominal design eye position for an operator wearing the NTE display50 provides a clear and unobstructed view of the outside scene, butslight motion away from the nominal position in any direction will causethe symbology overlay to be displayed. In another embodiment, thedirection of movement of dashed line 118 in FIGS. 5, 7, and 8 may bereversed, depending upon the tracked position along the y-axis. In yetanother embodiment, the luminance of the display may be changed abruptlywith orientation about the x-axis shown in FIG. 2, providing anuncluttered outside view when the display is in a first orientation(e.g., centered on the horizon line) but displays the full symbologywhen the the user's head is tipped forward and/or backward a smallamount (e.g. 3-5 degrees), which may be less than the instantaneousvertical field of view of the NTE display 50.

The symbology image 84 of FIG. 3 is also understood to not be limited toconventional symbology, and may also comprise or include such imagery assensor images, synthetic images, library images, conformal images or anyother content such as might obscure or distract from the image 82 ofFIG. 3.

Other embodiments may utilize the method and system described above onvehicles other than aircraft, such as land vehicles and watercraft. Themethod and system may also be used on unmanned vehicles, in which theoperational range limit corresponds to station where a user remotelycontrols the vehicle.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or exemplary embodiments are only examples, and arenot intended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing the exemplary embodiment or exemplary embodiments. Itshould be understood that various changes can be made in the functionand arrangement of elements without departing from the scope of theinvention as set forth in the appended claims and the legal equivalentsthereof

What is claimed is:
 1. A method for operating a vehicular near-to-eye (NTE) display screen operable within an operational range limit, the method comprising: rendering an image on the NTE display screen within a predefined visibility range, the predefined visibility range being within the operational range limit; and dynamically adjusting a luminance of at least a portion of the image in response to the NTE display screen being moved outside of the predefined visibility range and within the operational range limit, wherein the image includes symbology imagery and a luminance of at least a portion of said symbology imagery is dynamically adjusted in response to the NTE display screen being moved outside of the predefined visibility range and within the operational range limit.
 2. The method of claim 1, wherein the portion of the symbology imagery is non-conformal with an outside view.
 3. The method of claim 1, wherein the portion of the symbology imagery is neither terrain imagery nor representative of terrain imagery.
 4. The method of claim 1, wherein the at least portion of the symbology imagery includes one or more digital instruments, where each of said digital instruments is displayed in a particular corresponding position or portion of the NTE display screen.
 5. The method of claim 1, wherein the luminance of the at least portion of the image is dynamically reduced by approximately twenty-five percent.
 6. The method of claim 1, wherein at least one symbology imagery element in the image maintains a constant luminance regardless of the NTE display screen being moved outside of the predefined visibility range and within the operational range limit.
 7. A method for operating a near-to-eye (NTE) display screen operable within an operational range limit on-board an aircraft, the method comprising: causing a first image to be rendered on the NTE display screen within a predefined visibility range, wherein the first image is at least representative of a field of view of a user on-board the aircraft and the predefined visibility range is within the operational range limit and a function of at least three degrees of freedom; rendering a second image over the first image on the NTE display screen; and reducing a luminance of at least a portion of the second image in response to the NTE display screen being moved outside of the predefined visibility range and within the operational range limit, wherein the second image includes symbology imagery and a luminance of at least a portion of said symbology imagery is dynamically adjusted in response to the NTE display screen being moved outside of the predefined visibility range and within the operational range limit.
 8. The method of claim 7, wherein the portion of the symbology imagery is non-conformal with an outside view.
 9. The method of claim 7, wherein the portion of the symbology imagery is neither terrain imagery nor representative of terrain imagery.
 10. The method of claim 7, wherein the at least portion of the symbology imagery includes one or more digital instruments, where each of said digital instruments is displayed in a particular corresponding position or portion of the NTE display screen.
 11. The method of claim 7, wherein the luminance of the at least portion of the second image is dynamically reduced by approximately twenty-five percent.
 12. The method of claim 7, wherein at least one symbology imagery element in the second image maintains a constant luminance regardless of the NTE display screen being moved outside of the predefined visibility range and within the operational range limit.
 13. An avionics system comprising: a headset configured to be worn on a head of a user, the headset comprising a frame and a near-to-eye (NTE) display adjustably coupled to the frame to be positioned proximate to an eye of the user, the NTE display being operable within an operational range limit on-board an aircraft; a tracking system configured to detect at least one of a position and an angular orientation of the NTE display; and a processor in operable communication with the NTE display and the tracking system, the processor being configured to: render an image on the NTE display screen within the predefined visibility range, the predefined visibility range being within the operational range limit; and reduce a luminance of at least a portion of the image in response to the NTE display screen being moved outside of the predefined visibility range and within the operational range limit, wherein the image includes symbology imagery and a luminance of at least a portion of said symbology imagery is dynamically adjusted in response to the NTE display screen being moved outside of the predefined visibility range and within the operational range limit.
 14. The avionics system of claim 13, wherein the portion of the symbology imagery is non-conformal with an outside view.
 15. The avionics system of claim 13, wherein the portion of the symbology imagery is neither terrain imagery nor representative of terrain imagery.
 16. The avionics system of claim 13, wherein the at least portion of the symbology imagery includes one or more digital instruments, where each of said digital instruments is displayed in a particular corresponding position or portion of the NTE display screen.
 17. The avionics system of claim 13, wherein the luminance of the at least portion of the second image is dynamically reduced by approximately twenty-five percent.
 18. The avionics system of claim 13, wherein at least one symbology imagery element in the second image maintains a constant luminance regardless of the NTE display screen being moved outside of the predefined visibility range and within the operational range limit.
 19. The avionics system of claim 13, wherein the processor is further configured to reduce a luminance of at least a portion of the image in response to the NTE display screen being moved outside of the predefined visibility range and within the operational range limit and based upon the detected angular orientation of the NTE display.
 20. The avionics system of claim 13, wherein the processor is further configured to reduce a luminance of at the entire image when the NTE display is detected in a predetermined position and at a predetermined angular orientation. 